﻿// --------------------------------------------------------------------------------------------------------------------
// <copyright file="WindowCenteredPositionConverter.cs" company="http://buginbox.wordpress.com/">
//   Copyright (c) GNU General Public License version 2 (GPLv2)
// </copyright>
// --------------------------------------------------------------------------------------------------------------------

using System;
using System.Globalization;
using System.Windows.Data;

namespace Wpf.Core.Converter
{
    /// <summary>
    /// The window centered position converter.
    /// </summary>
    public class WindowCenteredPositionConverter : IMultiValueConverter
    {
        /// <summary>
        /// Converts source values to a value for the binding target. The data binding engine calls this method when it propagates the values from source bindings to the binding target.
        /// </summary>
        /// <param name="values">
        /// The array of values that the source bindings in the <see cref="T:System.Windows.Data.MultiBinding"/> produces. The value <see cref="F:System.Windows.DependencyProperty.UnsetValue"/> indicates that the source binding has no value to provide for conversion. 
        /// </param>
        /// <param name="targetType">
        /// The type of the binding target property. 
        /// </param>
        /// <param name="parameter">
        /// The converter parameter to use. 
        /// </param>
        /// <param name="culture">
        /// The culture to use in the converter. 
        /// </param>
        /// <returns>
        /// A converted value.If the method returns null, the valid null value is used.A return value of <see cref="T:System.Windows.DependencyProperty"/> . <see cref="F:System.Windows.DependencyProperty.UnsetValue"/> indicates that the converter did not produce a value, and that the binding will use the <see cref="P:System.Windows.Data.BindingBase.FallbackValue"/> if it is available, or else will use the default value.A return value of <see cref="T:System.Windows.Data.Binding"/> . <see cref="F:System.Windows.Data.Binding.DoNothing"/> indicates that the binding does not transfer the value or use the <see cref="P:System.Windows.Data.BindingBase.FallbackValue"/> or the default value. 
        /// </returns>
        public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
        {
            if (!(values[0] is double) || !(values[1] is double) || !(values[2] is double))
            {
                return null;
            }

            var containerSize = (double)values[0];
            var containerOffset = (double)values[1];
            var contentSize = (double)values[2];

            // Calculate position of content in container.
            var position = ((containerSize - contentSize) / 2) + containerOffset;

            return position;
        }

        /// <summary>
        /// Converts a binding target value to the source binding values.
        /// </summary>
        /// <param name="value">
        /// The value that the binding target produces. 
        /// </param>
        /// <param name="targetTypes">
        /// The array of types to convert to. The array length indicates the number and types of values that are suggested for the method to return. 
        /// </param>
        /// <param name="parameter">
        /// The converter parameter to use. 
        /// </param>
        /// <param name="culture">
        /// The culture to use in the converter. 
        /// </param>
        /// <returns>
        /// An array of values that have been converted from the target value back to the source values. 
        /// </returns>
        public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
        {
            throw new NotSupportedException();
        }
    }
}